Bleaching and treating of flour and agent therefor



Patentecl oct. 1c, 1939 PATENT? OFFICE 2475.112 memo AND mmrmc or norm. AND

mam-men AGENT I I Soul-en Z. Avedikian, New York, N. Y.

No Drawing. Application July 8, 1936,

/ Serial'No. 88,837

21 Claims. (01. 99 232) It is known that nitrogen oxides and certain compounds capable of liberating nitrogen oxides in contact with flour have been proposed as bleaches for flour. Nitrogen peroxide, N02, in

the gaseous form has been used successfully in -the past. As examples of known compounds capable of liberating nitrogen oxides in contact with flour, nitrosyl chloride, a gas, and nitrosyl sulfuric acid, a solid at ordinary temperatures,

may be mentioned. In contact with flour, they presumably react with the moisture present therein to give oxides of nitrogen and hydrochloric acid in the first case, and sulfuric acid' in the second.

It is recognized to be desirable from the viewpoint of the miller that the bleaching substance be in such a state that 'it can be used readily without hazard. The gaseous agents mentioned above involve danger to health, product and equipment unless proper precautionary measures are adopted in their use. carelessness on the part of the operator may have serious results.-

Those compounds which contain nitrogen oxides bound within their molecules, especially 5 those in the solid state, and which can be made to liberate itv when in contact with moisture,

have decreased the\hazar ds inherent in the use of nitrogen oxides, and have supplied the miller with a relatively easily applicable bleaching compound, possessing the peculiarly beneficial efiects of nitrogen oxides on flour. However, all these substances that have been mentioned for or used as bleaches have one characteristic in common.

5 That is, they all impart to flour an excess of one equivalent of acidity or more for each mole of oxide of nitrogen that is effective in the bleaching operation. Now, it is well known that excess acidity is undesirable in flour and that the pH of fiour must be maintained within certain definite limits in order to obtain optimum results in maturing and aging and in subsequent use in bread-making. Consequently, manufacturers of this type of bleach have adopted the expedient of mixing with their bleaching substances basic materials to rectify too high an acid condition and to obtain eventually, as nearly as possible, the proper acidity. v

The question of whether these alkaline substances are 'eftective'in neutralizing, in-situ, the

acidity produced may be debatable, but the danger exists that in the relatively dry, powdery state of flour, local acid or alkaline spouts or both will develop and will persist until the flour is made into dough. It is recognized that storage 5 of fiour under an excessively acid or a kaline conbleaching effect.

dition is harmful. Hence, in the use of these types of bleaches, there exists a period in the life of the fiour during which the pH is likely to be either too low or too high in certain places.

A second disadvantage is that the substances 5 capable of liberating nitrogen oxides, heretofore known and used as bleaches for flour, are extramely sensitive to moisture. They deteriorate readily in storage and very rapidly upon exposure to traces of moisture. Great care must be exer- 10 cised in their handling, otherwise their value in use is lost. This militates against their extensive 5, commercial application.-

A great many other substances have at various times been used as bleaches. Organic peroxides 15 are among these now most in favor, and they are usedin the form of a diluted dry powder. The miller addsa small percentage ofit to his flour and after about a day or two obtains the desired This ease of application has 2 made it attractive to the miller. Their manufacture, however, is attended with fire and explosion hazards; furthermore, the known methodsv of preparation are troublesome and costly. As a result, the bleaching compound is sold to the 25 millers at a high price.

Now I have found a newand useful treating agent for flour and othermilling products and have thus provided a new process suitable for the bleaching and improving of these food ma- 3o terials. My bleaching agent is an addition compound of sodium nitrite (or its equivalent) and sulfur trioxide, which upon mixing with fiour exerts a powerful bleaching effect upon it. It

seems probable thatthis fiour bleach acts by 35 liberating nitrogen oxides through decomposition by the water or moisture of the fiour.

The agent which I employ is a chemically different type of compound from formerly-known fiour bleaches capableof yielding nitrogen oxides, ,40 and possesses special advantages and distinctly superior qualities. Notwithstanding that it is an extremely active flour bleach, it isr'emarkably more stable in storage than the others, and preserves its strength for a much longer time; 45 nor does it attack the storage container.

Furthermore, it isgvery easily prepared, by a process which I have devised and will describe, from relatively -inexpensive starting materials, namely, sodium nitrite and sulfur trioxide. The 50 product of the reaction between these materials is a solid and can'be ground to a fine powder. It is non-toxic in use, acts on the color in the flour or the milling product, is highly efiective in whitening, and produces improvement in the quality of the flour. In bleaching by this method, the substances added are natural to flour. The residue of decomposition of this addition compound is neutral sodium sulfate, which does not appreciably affect the pH of the flour.

I have found that this flour bleaching agent can be successfully prepared by directly bringing together the ingredients, with agitation, and that the sulfur trioxide may be thus utilized in either the liquid or the gaseous state.

It appears that when sodium nitrite, or its equivalent, and sulfur trioxide are brought together a combination or union takesplace between them as follows:

NaNOz+n (S03) Na (S03) nNOZ where 12. may have any value from a small fraction to 3. z

The compound formed appears to be of the same general type of complex compounds to which certain ammonia complexes belong, e. g.,

cumin); Ag(NH3) z, Narnia); etc., in which the metallic ion behaves as if there were a number of ammonia molecules attached to it. In the present case, the addition compound behaves as if there were either a number of sulfur trioxide molecules attached to the sodium nitrite molecule or a number of sodium nitrite molecules attached to the sulfur trioxide molecule. I find that by my process of preparation I can put into the addition compound any quantity of sulfur trioxide less than three molecules. Thus, this compound can be made in various gradations by my process, such that sulfur trioxide varies from one. mole per two moles of sodium nitrite to one to one,

' etc. ghe former I have found to be preferred as a bleach for flour.

According to one form of my process for preparing a flour bleaching agent I may take 80 grams of sulfur trioxide in the liquid state and add to it slowly, with agitation, 69 to 138 grams of sodium nitrite, preferably well ground. Or, I may add the liquid sulfur trioxide slowly to the solid sodium nitrite first placed into the reaction chamber. The reaction producing the addition compound is highly exothermic. There-, fore, I prefer to keep the reaction chamber and it contents relatively cool by surrounding the vessel with cold water or a stream of liquid to dissipate the heat. I find that temperature of the surrounding medium between 15 and 40 ,C. at ordinary pressures are satisfactory, but other temperatures and pressures may be used. The

formation of this compound is rapid and the reaction reaches completion. in a relatively short time. I prefer, however, to let the reaction mixture stand for a few hours before further treatment. After about 3 4 hours or more, as the case may be, I remove the contents of the vessel, break up the coarse aggregates that may have formed, and, preferably after admixture with a water absorbing (or adsorbing) material, such as active clay, anhydrous sodium sulfate, anhydrous calcium sulfate, colloidal silica, si ica gel, etc., I grind it to a fine powder. This fine powder acts as an effective bleach and improver for flour. The color of flour is lightened considerably and the resulting bread has a lghter appearance and the loaf is larger in volume than ordinarily. i

As an alternative procedure, place 69 to 138' grams of sodium nitrite in a reaction chamber which is equipped to maintain the solid substance in a state of constant agitation, either by tumbling as in a ball mill or a tumbling mixer,

I jacket, etc.

' for the productionof a dry powdery substance water or moisture liberates nitrogen oxides. The

or by means of a rotating agitator within a stationary shell. The chamber should preferably be designed to dissipate the heat of the reaction quickly and effectively as by a cooling-water Then, after the agitation has been started, lead into the chamber a stream of sulfur trioxide in the gaseous state, either pure undiluted sulfur trioxide or this gas diluted with an inert gas such as air, nitrogen, carbon dioxide, etc. The term inert" is used here in the sense that the dilut gas does not itself take part in the reaction but is instrumental merely in supplying sulfur trioxide in smaller quantities than would otherwise be possible, in the event that a slower and a better controlled reaction with sodium nitrite is desired. When the required amount of sulfur trioxide has been passed into the reaction chamber, 1. e., to produce a compound from 1:1 to 251 in ratio with respect to sodium nitrite and sulfur trioxide as desired, discontinue the stream of sulfur trioxide and allow the mixture to stand fora few hours and then grind it to a fine powder in the presence of a water absorbent material such as anhydrous sodium sulfate, silica gel, etc., singly or in combinations of two or more;

The following are specific examples;

Example I Sulfur tr Sodium! nitr te Sodium sulfate (anhydrous) 16 Example II Parts Sulfur trioxide 0 Sodium nitrite 138 Sodium sulfate (anhydrous) 24 The reaction and the subsequent operations may be carried out as described under Example I.

The quantities and substances above mentioned are in accordance with the preferred embodiment of that part of my invention which involves the preparation of the addition compound, which I have discovered to be valuable as a flour bleach. I have found, however, that variations within the quantities above specified and also outside those quantities are possible capable of bleaching flour. The ratio of sodium nitrite to sulfur trioxide may vary from 1:2 or less to 2: 1 and-even higher, for example 4:1, with a resulting-product which upon reacting with liberation of oxides of nitrogen, however, does not appear to be complete when the ratio is greater than 2: On the other hand, the bleaching effect of the compound on flour and the like would be considerably diminished if the ratio should closely approach 1:3. 5 All such variations are intended to be within the scope of this invention.

The foregoing description and the examples given above have mentioned sodium nitrite. This has been done merely for the sake of clarity in the exposition and with no intention of limiting myself .to the use of sodium nitrite solely. The nitrites of lithium, potassium, andcalcium, i. e., those which are capable of forming an addition compound with sulfur trioxide analogous to that of sodium nitrite, are equivalents of sodium nitrite for the purpose of my invention.

The process of bleaching flour or other milling product with the herein described material is'to mix a small amount of the bleach with the milling product, after which the thus-treated flour is allowed to stand. Suitable proportions are 1 part of the mixture of Example I, finely ground, with 7,000 parts of flour. The resulting flour has a most desirable quality of whiteness. It also has a greater water absorption value than ordinary flour and the bread produced therefrom is of a finer texture than that which would be produced from the untreated flour.

Having thus broadly outlinedmy invention, and having specifically mentioned the substances that I use in the preferred embodiment of my invention, and method of application thereof, I claim the following:

1. The process of treating flour and other milling products to bleach the same, which comprises mixing therewith an addition compound of sulfur trioxide and the nitrite of a metal of the group consisting of lithium, sodium, potassium, and

calcium.

2. The process of treating flour and other milling products to bleach the same, which comprises mixing therewith an addition compound of sulfur trioxide and sodium nitrite.

3. The process of treating flour and other milling products to bleach the same, which comprises mixing therewith an addition compound of sulfur trioxide and the nitrite of a metal of the group consisting of lithium, sodium,- potassium, and calcium, utilizing as such bleaching agent a compound in which there are less than 3 molecular parts of sulfur trioxide to 1 part of the nitrite.

4. The process. of treating flour and other milling products to bleach the same, which comprises mixing therewith an addition compound of sulfur trioxide and the nitrite of a metal of the group consisting of 'lithium, sodium, potassium, and calcium, utilizing as such bleaching agent a compound in which the ratio of the nitrite to sulfur trioxide is between substantially 1:2 and 2:1.

5. The process of treating flour and other milling products to bleach the same, which comprises mixing therewith an addition compound of sulfur trioxide and the nitrite of a'metal of the group consisting of lithium, sodium, potassium, and calcium, utilizing as such bleaching agent a compound in which the ratio of the nitrite to sulfur trioxide is approximately 2:1.

6. The process of treating flour and other milling products to bleach the same, which comprises mixing therewith an addition compound of sulfur trioxide and sodium nitrite, in which compound the ratio of sodium nitrite to sulfur trioxide is approximately 2:1.

7. A bleaching agent for flour and milling products, comprising. a complex. addition compound formed by the reaction of sulfur trioxide with the nitrite of a metal of the group consisting of lithium, sodium, potassium and calcium, in which there is less than 3 molecular parts of the trioxide to 1 part of the nitrite and more than 1 of sulfur trioxide to 4 parts of the nitrite, which upon admixture with flour and milling products produces a lightening of the color thereof.

8'. A bleaching agent for flour and milling products, comprising the addition compound of sulfur trioxide and the nitrite of a metal of the group consisting of lithium, sodium, potassium and calcium formed by the reaction between the trioxide and the nitrite, wherein the ratio of the nitrite to sulfur trioxide is between substantially 1:2 and 2:1, which upon admixture with flour causes a lightening of the color thereof.

9. The process 'of treating flour and milling products to bleach the same, which comprises adding thereto and mixing therewith a compound having the formula R(S O3)xN0z, wherein R. represents a metal of the group consisting of sodium, lithium, potassium and calcium, and a: is less than 3.

10, The process of treating flour and milling products to bleach the same, which comprises mixing therewith a compound having the formula I N8.(SO3)XNO2, wherein a: is less than 2.

11. A bleaching agent for flour and milling products having the formula R(SO3) N02, wherein R represents a metal of the group consisting of sodium, lithium, potassium and calcium.

12. The process of treating flour and milling products to bleach the same, which comprises adding thereto and mixing therewith a compound having the formula (R)x(SOa) (N02)x, wherein R represents a metal of the group consisting of sodium, lithium, potassium, and calcium, and .2: equals 2 to 4.

13. The process of treating flour and milling products to bleach the same, which comprises adding thereto and mixing therewith a compound having the formula (Na) a(SO3) (NO2)2.

14. A bleaching and maturing agent for flour the formula thereon,

17. The process of treating flour and other milling products which comprises mixing therewith an addition compound of sulfur trioxide and sodium nitrite, in which compound the ratio of sodium nitrite to sulfur trioxide is between substantially 1:2 and 2:1, to effect maturing thereof.

18. The process of treating flour and other milling products, which comprises mixing therewith an addition compound of sulfur trioxide and sodium nitrite, in which compound the molecular ratio of sodium nitrite to sulfur trioxide is approximately 2:1, toeifect maturing thereof.

19. A maturing agent for flour and milling products, comprising a complex addition compound formed by the reaction of sulfur trioxide with the nitrite ofa metal of the group consisting of lithium, sodium, potassium and calcium,

in which there isless than 3- molecular parts of the trioxide to 1 part of the nitrite and more than 1 part of sulfur trioxide to 4 parts of the nitrite, which upon admixture with flour and milling products produces a maturing effect thereon.

20. A'maturing agent for flour and products, comprising the addition compound of sulfur trioxide and the nitrite of a. metal of the group consisting of lithium, sodium, potassium and calcium formed by the reaction between the trioxide and the nitrite, wherein the ratio of the nitrite to sulfur trioxide is between substantially 1:2 and 2:1, which upon admixture with flour and.

milling products produces a maturing efiect thereon.

21. A maturing agent for flour and milling products, having the formula R(SO3) N02, wherein R. represents a metal of the group consisting of sodium, lithium, potassium and calcium.

' SOUREN Z. AVEDIKIAN. 

